Deposition Ice Nuclei Observations over the Indian Region during CAIPEEX

A thermal gradient diffusion chamber (TGDC) designed to process the ice nuclei (IN) samples are illustrated with unique observations. IN samples collected during the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) have been analysed using the TGDC. The TGDC is able to activate the IN by deposition mode over ice supersaturation of 6-25% and at a temperature range of -18.5 to -13.5 oC. These samples correspond to first time observations at several vertical levels including the cloud layer and over several geographically distinct locations in India during the monsoon season. IN samples were analysed by adjusting the temperature difference between the plates. Vertical profile of IN concentration shows large spatial variation at each level. Highest IN concentrations are noted over inland continental regions. Spatial variation in IN concentration was observed in the range 0 to 5 L-1 with an average of 1.5 L-1. Large variation in IN concentration at a single temperature is also observed. Our observation shows that there is significant increase in IN concentrations with supersaturation over ice. Elemental chemical analysis of the samples by SEM-EDX showed that Copper, Silica, Aluminium and Zinc are the most abundant elements.